Show only the shadow of units

Achieving such an effect really isn't that hard. Simply follow this little step-by-step tutorial.

The steps

1. Select the actor of the unit you want to only show the shadow for
2. Go to the Events section of the actor
3. Right click anywhere in the left hand box and select Add Event
4. Change the Msg Type to Actor Creation, leave all other fields as any
5. Select the action (the item below directly below the one selected)
6. Change Msg Type to Set Opacity
7. Change Opacity to 0.0001

Note: Setting Opacity to 0 will not render any shadow, which isn't what we want.